The present invention relates to a process and a system for recovering top gas from a blast furnace or the like.
In general, the operation of a blast furnace is carried out almost under high pressure in order to attain stabilized high productivity.
To this end, the inside of the blast furnace is communicated with the surrounding atmosphere through a hopper whose pressure is increased or decreased in such a way that the materials may be charged into the blast furnace under the same pressure as the top pressure.
In order to equalize the pressure in the hopper with the atmospheric pressure, the top gas has been in general discharged into the surrounding atmosphere through a top gas discharge duct or the like. However, the top gas contains not only a large amount (on the order of 0.3 kg/Nm.sup.3) of CO which is hazardous to the health of human beings but also a large amount (on the order of from 10 to 30 g/Nm.sup.3) of dust. Furthermore, the materials are charged into the blast furnace in general from 500 to 800 times a day and the volume of the top gas discharged amounts to 1000 Nm.sup.3 per charge with the discharge of CO gas and dust of 200 and 15 tons, respectively. As a result, the pollution of the atmospheric air and the high-level noise produced when the top gas is discharged present very serious environmental problems. In addition, in view of the ever increasing serious energy problems, it is very uneconomical to discharge the top gas which may be burned as a fuel.
The present invention was made to overcome the above and other problems encountered in the blast furnaces which discharge the top gas to the surrounding atmosphere without any suitable processing and thermal utilization, and will become apparent from the following description of some preferred embodiments thereof taken in conjunction with the accompanying drawings.